Is there a formula to calculate the standard deviation of a group or individual statistics
Example in a sporting fantasy league I can calculate the summary statistics of any one player.
one player has a Mean 75, Standard deviation 26.
But what if I selected a group of 18 players with the same summary stats, can I estimate the summary statistics of this group?
The Mean I believe can just be multiplied 1350 (75*18),
but the standard deviation isn't as simple as using a multiplication?
To add to this- if the group of 18 players each had unique summary stats, can the groups summary stats also be explained/calculated? example
Player 1 - mean 75 sd 26 Player 2 - mean 100 sd 28 Player 3 - mean 105 sd 25 . . Player 18 - mean 72 sd 23
Any help would be great.